Vertical tubular heat exchanger



May 3, 1949. E. VlLLlGER 2,463,903

VERTICAL TUBULAR HEAT EXCHANGER Filed Aug. 28, 1946 lnu enior EugenVilliger I By I Fig AFtorpcga Patented May 3, 1949 UNITED STATE VERTICALTUBULAR HEAT EXCHANGER Eugen Villiger, Zurich, Switzerland, assignor toAktieng'esellschaft Fuer Technisehe Studien,

Zurich, Switzerland,

a corporation of SWIIGI'! land Application August 28, 1946, Serial No.693,451 In Switzerland September 22, 1945 1 Claim. (01. 257-222) 2 Thisinvention relates to a vertical tubular to be heated passes firstthrough the said annular heat exchanger in which a medium is to beheated on the contraflow principle by flue gases which arrive at aconsiderable height above ground.

Tubular heat exchangers of this kind are erected for example in thermalpower plants of the type, in which the working medium traverses a closedcycle and heat derived from an external source is to be supplied to thisworking medium indirectly by a main combustion heater. Combustionheaters for plants of this kind are usually of considerable height, andthe flue gases frequently leave the heater at the upper end thereof sothat they emerge at a considerable height above ground. Particularly inheaters which are fired with oil or pulverised coal the fresh airrequired for the support of combustion has then likewise to be suppliedfrom above to the burners arranged in the upper part of the heater. Iftherefore a preheater for theair required for the support of combustionhas to be erected in conjunction with a combustion heater of this kind,so that said air shall be heated therein by the waste gases arrivingfrom the combustion heater, the connections on the air preheaterprovided for the incoming flue gases and the outgoing heated air arepreferably placed at the top of the preheater, since an arrangement ofthis kind permits of long connecting pipes being dispensed with. Thefresh air to be heated in the preheater is advantageously drawn off fromthe upper part of the engine room as the temperature near the ceiling ofthis room is higher by a few degrees than that directly above the floor.

In connection with tubular heat exchangers of this kind, used as apreheater, the problem arises of how to make it'possible to bring aboutin a vertical tube nest an exchange of heat between the fresh air thatis to be heated and the heat of the outgoing flue gases on thecontraflow principle, and also how to utilise the thermal content of thewaste gases issuing from the combustion heater to as great an extent aspossible for the heating up of the air required for the support ofcombustion. In order to satisfy these various requirements, the problemsabove referred to are solved according to the present .invention bybuilding into a tubular heat exchanger of the kind above describedconcentrically with a tube nest firstly achimney tube as the innermostbody and then a second tube which surrounds the latter and leaves anannular space round it free. In this arrangement the medium space, andthe flue gases which issue from the said tube nest and have been alreadybrought therein to a lower temperature, pass in the op- 5 posite'direction to said medium through the chimney tube on the contraflowprinciple thereby giving up still more heat'to the medium to be heated.

When the present invention is used no separate high chimney stack withits own foundation needs to be provided. The type of constructionemployed according to the present invention also enables the heat oftheescaping flue gases to be utilised to a very large extent, which isfavourable from an economical point of view.

A constructional form of the subject matter of the invention isillustrated by way of example in the accompanying drawings in which:

. Fig. 1 shows on an enlarged scale an axial longitudinal sectionthrough said tubular heat exchanger, and

Fig. 2 shows in the'left hand half a section on the line IIII of Fig.1and in the right hand half a plan view of Fig. 1.

The structure illustrated in Figs. 1 and 2 is not the main combustionheater. but is a preheater used to derive heat from combustion productsdischarged by the'main combustion heater (not shown), near the topthereof and hence at a substantial elevation, and transfer said heat tocombustion air flowing to the main combustion heater.

The numeral l5 denotes the cylindrical shell of the preheaterconstructed as a vertical tubular heat exchanger, in which fresh airentering through a connection is is to be heated in a vertical tube nestI! by the exchange of heat with flue gases. These latter are derivedfrom the main combustion heater. These flue gases, which arrive at aconsiderable height above ground, en ter from above through a connection18 (Fig. 1) into the interior of the shell l5 of the heat exchanger andpass from the top downwards through the tubes of the nest I! which isannular in cross section. A chimney tube l9, part of which extends abovethe shell l5 of the heat exchanger, forms the innermost body of thislatter and is built into the heat exchanger coaxially with the tube nestl'l. Into the heat exchanger is also built a second tube 20, whichsurrounds the chimney tube l9 and leaves an annular space 2| betweensaid chimney tube and itself. The fresh air entering through the tube l6passes from the top downwards through the annular space 2|, while theflue gases, which escape at the bottom of the tubes of the nest i1 andin which they have been cooled down already to a great extent, passthrough the chimney tube I! from the bottom upwards. In this way anexchange. of heat with the fresh air flowing in the opposite directiontakes Place, so that the flue gases become cooled down still further asthey pass through the chimney tube l9, that is to say more heat isabstracted from them which however is usefully employed for heating upthe fresh air which has entered through the connection It. The fresh airpreheated in the annular space 2| passes at the bottom into the tubenest l1, flows around the tubes of this nest in the opposite directionto the flue gases and finally emerges in a heated state through theconnection 22 near the top of the heat exchanger, after which it isconducted to the burner of the main combustion heater (not shown).

The, lower supporting plate 25 to which the lower ends of the tubes ofthe nest i1 and the chimney tube IQ of the heat exchanger are fas'-tened, is rigidly mounted, since it comes into con tact withcomparatively cold gases only. The plate 25 is also supported by anumber of columns 28 so that it may be comparatively hin which isdesirable from the standpoint of thermal stresses and the large numberof holes which have to be drilled in it. The top plate 21 of the tubenest I1 is on the other hand connected to the shell 15 by an elasticlength of tube 28 so that it can expand upwards. As therefore this plate21 is not subjected to any additional stress due to thermal expansion,it may be thin so that it can more easily follow any unequal thermalexpansions which may possibly take place. the chimney tube [9 is alsoconstructed as a piece of elastic tube. 7

What is claimed is:

A vertical tubular heat exchanger, in which a medium is to be heated onthe contrafiow principle by flue gases which arrive at a considerableThe part 29 of height above ground, comprising a vertical cylin dricalshell; a vertical tube nest built into said shell and comprising anupper and lower plate into which the tubes of this nest are fixed; anupper header provided at the top end of said shell and having an inletfor flue gases, said header serving to distribute said gases over theupper extremity of the tubes of said nest; a lower header incommunication with said tubes; a chimney tube built into said shellcoaxially with said tube nest as the innermost body, in communicationwith said lower header and leading to a point external to the heatexchanger; a second tube surrounding said chimney tube and leaving anannular space between the, latter and itself and communicating at itslower end with the space which is bounded by said shell, said upper andlower plates of the tube nest and said chimney tube; a second inletprovided at the top of said shell for the incoming medium to be heatedand connected to said second tube; and an outflow connection for heatedair leading from the upper end of the space bounded by the shell, theupper and lower plates of said tubenest and they chimney.

EUGEN VILLIGER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 752,994 McKee Feb. 23, 19041,142,495 Clisdell June 8, 1915 1,856,771 Loefller May 3, 1932 FOREIGNPATENTS Number Country Date 17,255 Great Britain July 24, 1909 41,206Germany Oct. 18, 1887

